I have my 1970 d100 stripped right to the frame for a full restoration; the slant 6 will get a refreshening and is on the engine stand.
I have the 4 speed manual transmission in the truck from the factory, and up until I disassembled the truck it operated perfectly. I'm pretty sure the tranny hasn't been touched since new, so I am wondering since it is out of the truck and on the work bench, what would you guys suggest I do as far as freshening up the tranny? I was thinking a gasket and seal kit but I have only ever worked on automatics and am open to suggestions from people who know more about them than I do as to how I should proceed. I am pretty much if it aint broke, don't fix it guy but then again with the entire truck apart it would be crazy not to do at least a basic maintenance on the tranny.
Opinions if this was your truck gents?

They don't generally break, but they do wear out. I recommend you pull the tower and have a look at the gears. If all appears ok, then you can use silicone to seal it up. I pulled mine apart only to find it worn out, was going to be about 700 dollars in parts to fix it. I'm going the 4500 route.